BackTrack 5

"BackTrack is intended for all audiences from the most savvy security professionals to early newcomers to the information security field. BackTrack promotes a quick and easy way to find and update the largest database of security tools collection to-date. Our community of users range from skilled penetration testers in the information security field, government entities, information technology, security enthusiasts, and individuals new to the security community."

http://www.backtrack-linux.org/
http://www.backtrack-linux.org/downloads/

http://www.backtrack-linux.org/wiki/
http://www.backtrack-linux.org/wiki/index.php/FAQ